Every week, about 21% of U.S. workers take some form of time off, either unpaid or paid. The average time off is 15.6 hours per week, or roughly two standard 8-hour work days.

Laid off by NASA, now cutting grass

Vacation is the most common reason for taking days off, with personal illness falling in a close second.

Lower income workers are more likely to take sick days, whereas high income earners are more likely to take vacation days.

The "Access to and Use of Leave" report is a one-time study conducted by the U.S. Department of Labor and does not compare data over a historical period.

The report comes as advocates in major cities have been pushing for sick leave laws. Some New York City Council members are currently pushing for a law that would require employers to allow workers to earn a minimum of five to nine sick days a year, depending on the size of the business.

Connecticut passed a similar statewide law last year, requiring some businesses to give their employees paid sick leave. Seattle, San Francisco and Washington, DC have similar city ordinances already in place,although the details vary by city.